backlight: hx8357: Utilise temporary variable for struct device

We have a temporary variable to keep pointer to struct device.
Utilise it inside the ->probe() implementation.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20240201144951.294215-5-andriy.shevchenko@linux.intel.com


Signed-off-by: Lee Jones <lee@kernel.org>